So this is what I have. did some research, so this is what I believe it to be. Conn Organ 2 channel amp (has 2 gain pots, 2x 12ax7, 4x 7868)
2x cletron 12" alnico speakers
1x Jensen Oxford 8"
32x RCA 12au7 clear top grey plate side square getters
I talked to a local tube guy who will put some rca jacks and 5-ways on it, check/ change necessary parts to get it running good, willing to trade work for some of the tubes or speakers I got. Do you know what the 12au7 and speakers are worth? I guess I don't have any use for them anyways.
another question, will this amp power my Martin Logan aerius electrostatic panels? they are small and bi-ampable.
please change thread title to Salvaged Conn 7868 Amp
2x cletron 12" alnico speakers
1x Jensen Oxford 8"
32x RCA 12au7 clear top grey plate side square getters
I talked to a local tube guy who will put some rca jacks and 5-ways on it, check/ change necessary parts to get it running good, willing to trade work for some of the tubes or speakers I got. Do you know what the 12au7 and speakers are worth? I guess I don't have any use for them anyways.
another question, will this amp power my Martin Logan aerius electrostatic panels? they are small and bi-ampable.
please change thread title to Salvaged Conn 7868 Amp
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finally got my hands on the capacitors for this amp from a local store. I don't have test equipment or real knowledge so I just bought all the caps and replaced them. I knew I had a bad tube so I was gonna run mono and check each side. while switching tubes around I noticed the amp runs and sounds excellent with only 1 output tube in each channel. are these run in parallel? I thought the amp was PP and needed both tubes to operate.
Also, the amp has two output leads per OT. one yellow one green (plus a black). the transformer part no. is k-58459 606-6-03. I am assuming these are 8 and 16 ohm leads, I don't have a schematic. Is there any way I can tell which is which with my multi-meter?
Also, the amp has two output leads per OT. one yellow one green (plus a black). the transformer part no. is k-58459 606-6-03. I am assuming these are 8 and 16 ohm leads, I don't have a schematic. Is there any way I can tell which is which with my multi-meter?
FYI, that is a stereo amplifier. You can see the other output transformer under the chassis. Is in in fact push/pull. Removing one tube in a push/pull configuration will not render it inoperable, but it will diminish the sound and in some circumstances, it will cause the one tube to redplate without the load of the other tube. Sometimes it will also cause unwanted hum.
In push/pull, technically, one tube is pushing while the other one is pulling or one tube is negative and the other tube is positive.
In push/pull, technically, one tube is pushing while the other one is pulling or one tube is negative and the other tube is positive.
Thanks for the response! I bought a quad of new in box sylvania today for 100.00. This amp is driving martin Logan's aeriusI speakers and it sounds glorious. I am truly amazed. As far as the leads go, I'm going to make them both accessible and play it by ear.
There are two of these on fleabay right now, one for 45.00 and one for 119.00. Can bridge this amp and make it mono at 72 watts and 4 ohm? These Logan's are hungry, plenty loud now, but want way more.
There are two of these on fleabay right now, one for 45.00 and one for 119.00. Can bridge this amp and make it mono at 72 watts and 4 ohm? These Logan's are hungry, plenty loud now, but want way more.
It's not really a bridgeable amp persay but some tube amps can be paralleled at the outputs to make a single channel. Look at the mono Bogen MO-200A amplifier. It parallels its output transformers in its design.
Your amp uses the 7868 tube which is similar in operational statistics to the 7591 tube. In push pull configuration, your amp give about 35-40 watts each channel.
I don't know your level of expertise, but people like to convert these amps into mono push/pull/parallel configuration but this requires a knowledge of the circuit plus you would need a bigger single output transformer to handle the load.
Your amp uses the 7868 tube which is similar in operational statistics to the 7591 tube. In push pull configuration, your amp give about 35-40 watts each channel.
I don't know your level of expertise, but people like to convert these amps into mono push/pull/parallel configuration but this requires a knowledge of the circuit plus you would need a bigger single output transformer to handle the load.
Hi all!
Been a while so I wanted to update this thread a little and maybe ask a few questions.
I'll start with what I love about this amp. As I mentioned I am driving Martin Logan Aerius I's with it. I like electrostats and until now have only used SS amps to drive them. this amp makes them transistor amps sound like they were made from soup cans and tinfoil. My Luxman M-117 is now on permanent loan to a friend. Vocals, horns, and especially ORGANS seem to bloom and blossom out of my speakers like a kaleidoscope for my ears. I can hear the difference between pre amp and power amp distortion on recordings. listening to the Allman Brothers "goin down slow", the lead guitar rips through the room like its live, and it sounds like its gonna break my system, even at lower levels you can fully hear the torture Duane is putting that amp through. Awesome. The music is shimmering with electricity.
I love this amp so much I bought another one. They are now twins with pretty much all the same components, including new caps.
I have hooked these up numerous ways. my speakers are bi-ampable. so I hooked them up in stereo: singularly, bi-amped with one for highs and one for lows, bi-amped with one for each speaker, as mono blocks using only one channel each amplifier (unused channel tubes removed), and utilized the 4 and 8 ohm output taps in each configuration. After a lot of listening I really cant hear much difference between all of this and am running just one amp in stereo bi-wired now, from the 4 ohm taps (these do match my speakers better and I can hear a difference between 4 and 8 ohm taps as the 4 ohm are a little louder). Again most differences were so subtle, to me they just aren't worth burning the extra Sylvania tubes up.
then I started reading about PPP. great. Reading all I could find on this I gathered that I could feed the same signal to both channels, parallel the outputs, and get twice the watts. I understand the 4 ohm taps would then be 2 ohm, and the 8 ohm would be 4. So I hooked them up this way, and BOOM! Just kidding. They sounded a little louder and a little tighter. Been that way for a week or so with no problems.
1. Am I really getting twice the watts with the outputs wired in parallel?
I have only one issue with them and that is the high frequency response. Cymbals seem to roll off pretty sharp over 12khz. I can hear them, but they seem to be lower in volume and like they have felt on them killing the "sizzle".
I was considering changing them to mono PPP, though I like the versatility of two matching stereo amps. So I did some research, and found the Hammond 1650ha for stereo PP use (6,600 ct, 40w) and the 1650ka for mono PPP (3,400 ct, 50w). I don't know if 50w is enough for this amp in PPP as I don't know how many watts it puts out. I have read 20-30 different sources that say from 18-40w per channel with most being 24-28w. Also, the OPT's on the Conns only have 3 wires going into them. The Hammonds have 5.
2. Are the Hammond transformers compatible with my amp?
3. can I make the Stereo/mono switchable like an ST-70?
MOST IMPORTANTLY:
4. Will you help me build these?
Thanks for all the responses, any and all opinions and suggestions are greatly appreciated. here is a schematic I found (pain in the a**). I figure it should be here incase anyone is inclined to help me, or if someone is searching as I was. Thanks again. -vince
Been a while so I wanted to update this thread a little and maybe ask a few questions.
I'll start with what I love about this amp. As I mentioned I am driving Martin Logan Aerius I's with it. I like electrostats and until now have only used SS amps to drive them. this amp makes them transistor amps sound like they were made from soup cans and tinfoil. My Luxman M-117 is now on permanent loan to a friend. Vocals, horns, and especially ORGANS seem to bloom and blossom out of my speakers like a kaleidoscope for my ears. I can hear the difference between pre amp and power amp distortion on recordings. listening to the Allman Brothers "goin down slow", the lead guitar rips through the room like its live, and it sounds like its gonna break my system, even at lower levels you can fully hear the torture Duane is putting that amp through. Awesome. The music is shimmering with electricity.
I love this amp so much I bought another one. They are now twins with pretty much all the same components, including new caps.
I have hooked these up numerous ways. my speakers are bi-ampable. so I hooked them up in stereo: singularly, bi-amped with one for highs and one for lows, bi-amped with one for each speaker, as mono blocks using only one channel each amplifier (unused channel tubes removed), and utilized the 4 and 8 ohm output taps in each configuration. After a lot of listening I really cant hear much difference between all of this and am running just one amp in stereo bi-wired now, from the 4 ohm taps (these do match my speakers better and I can hear a difference between 4 and 8 ohm taps as the 4 ohm are a little louder). Again most differences were so subtle, to me they just aren't worth burning the extra Sylvania tubes up.
then I started reading about PPP. great. Reading all I could find on this I gathered that I could feed the same signal to both channels, parallel the outputs, and get twice the watts. I understand the 4 ohm taps would then be 2 ohm, and the 8 ohm would be 4. So I hooked them up this way, and BOOM! Just kidding. They sounded a little louder and a little tighter. Been that way for a week or so with no problems.
1. Am I really getting twice the watts with the outputs wired in parallel?
I have only one issue with them and that is the high frequency response. Cymbals seem to roll off pretty sharp over 12khz. I can hear them, but they seem to be lower in volume and like they have felt on them killing the "sizzle".
I was considering changing them to mono PPP, though I like the versatility of two matching stereo amps. So I did some research, and found the Hammond 1650ha for stereo PP use (6,600 ct, 40w) and the 1650ka for mono PPP (3,400 ct, 50w). I don't know if 50w is enough for this amp in PPP as I don't know how many watts it puts out. I have read 20-30 different sources that say from 18-40w per channel with most being 24-28w. Also, the OPT's on the Conns only have 3 wires going into them. The Hammonds have 5.
2. Are the Hammond transformers compatible with my amp?
3. can I make the Stereo/mono switchable like an ST-70?
MOST IMPORTANTLY:
4. Will you help me build these?
Thanks for all the responses, any and all opinions and suggestions are greatly appreciated. here is a schematic I found (pain in the a**). I figure it should be here incase anyone is inclined to help me, or if someone is searching as I was. Thanks again. -vince
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